The boysenberry is a complex hybrid fruit belonging to the Rubus genus, a cross that includes the European raspberry, the European blackberry, the American dewberry, and the loganberry. This large, reddish-purple berry is highly valued for its sweet-tart flavor and soft texture. Boysenberry plants can possess thorns, especially in their original form. However, the vast majority of boysenberries sold commercially today are propagated from thornless selections.
The History of Boysenberry Thorns
The presence of thorns in the original boysenberry plant is a direct result of its complex genetic inheritance. The initial hybrid, developed by Rudolph Boysen in the 1920s, inherited the thorny characteristic primarily from its blackberry and dewberry lineage. Blackberries, a major component of the parentage, are naturally armed with sharp prickles. The earliest cultivated vines, commercialized by Walter Knott, were of this original thorny type.
These original thorny canes presented significant challenges for commercial growers due to the difficulty of pruning and harvesting the delicate fruit. Horticulturalists began breeding efforts to isolate and propagate mutations that lacked these sharp projections.
A major breakthrough occurred with the development of specific thornless strains, such as those that came out of New Zealand breeding programs in the 1980s. These newer cultivars were often developed using tissue culture techniques to ensure the desired characteristics were maintained. This successful removal of the prickles led to the widespread adoption of the thornless varieties for both large-scale commercial farming and home gardening.
Identifying Thornless Cultivars
Identifying a thornless boysenberry cultivar begins with the labeling at nurseries, where they are typically sold explicitly under names like ‘Thornless Boysenberry’ or a specific thornless variety. The physical examination of the canes offers the most reliable field identification method.
Thornless boysenberry canes are generally smooth to the touch, lacking the rigid, sharp projections found on their thorny counterparts. This absence of prickles makes the processes of pruning, training, and harvesting the trailing vines significantly easier for the home gardener. The vine-like growth habit of the boysenberry, regardless of thorn presence, necessitates support systems like trellises or wires for best results.
Some thornless varieties are not perfectly spineless and are better described as “nearly thornless.” Furthermore, a thornless plant occasionally exhibits a genetic phenomenon where a cane, especially one growing directly from the root crown, reverts to the original thorny state. These rogue thorny canes should be pruned out immediately to prevent the plant from diverting energy to the less desirable growth.
Boysenberries Versus Other Cane Berries
Boysenberries belong to the bramble group, which includes their close relatives, the true blackberries and raspberries. The canes of the original thorny boysenberry tend to have prickles that are less dense than those found on many wild blackberry species. Wild blackberries are notorious for having long, aggressive, and numerous thorns that make movement around the plants difficult.
Red raspberries also possess thorns, but these are generally smaller and more hair-like than the sharp spines of a thorny blackberry. The boysenberry’s thorns, when present on older varieties, are often described as being intermediate—between the raspberry’s fine prickles and the blackberry’s larger spines.